JPWO2013061391A1 - Electric power steering device - Google Patents

Abstract

The electric power steering apparatus includes a monitoring control unit that monitors a CPU abnormality and controls a drive signal for driving the motor when the CPU abnormality occurs. The monitoring control unit includes a first control mode for stopping the driving of the motor. There is a second control mode in which the motor is continuously controlled by a provisional drive signal that restricts the drive signal instead of the CPU drive signal. When the monitor control means detects an abnormality in the CPU, the monitor control means selects the second control mode. Then, the motor is continuously controlled by a provisional drive signal in place of the CPU drive signal, and after the control in the second control mode, the first control mode is selected to stop the motor drive.

Description

  The present invention relates to an electric power steering device that drives and controls a motor based on a steering torque of a driver and reduces the steering torque of the driver by power generated by the motor.

  The electric power steering device realizes a function of driving a motor in accordance with information such as a steering torque signal and a vehicle speed to reduce a driver's steering force. When an abnormality occurs in a main CPU (Central Processing Unit) that controls the motor, it is necessary to limit the output of the motor in order to ensure safety. On the other hand, as a method of limiting the motor output regardless of whether the main CPU is abnormal or not, a range in which the output is prohibited is defined for the relationship between the (steering) torque signal and the motor drive current signal, In some cases, there is a method using so-called interlock means for prohibiting motor output. Alternatively, there is a method of providing a sub CPU that monitors the main CPU that controls the motor, and stopping energization of the motor when the sub CPU detects an abnormality in the main CPU.

  Furthermore, when the motor drive is stopped, it becomes difficult to rotate the steering wheel, and there is a possibility that the vehicle itself cannot travel. Therefore, there are some that perform continuous control as much as possible according to the content of the failure. For example, when the main torque signal is abnormal, the control is continued using the sub torque signal.

Japanese Patent No. 3285490 JP 200326024 A JP 2005-271860 A

In the system of Patent Document 1, a range in which output is prohibited is determined for the relationship between the torque signal and the motor drive current signal, and when the output is in the output prohibition range, a method using a so-called interlock means for prohibiting motor output. It was. The interlock means limits the output of the motor, but does not determine whether the CPU is abnormal. Therefore, the CPU continues to drive the motor in an abnormal state until the driver turns off the ignition key.

  In the system of Patent Document 2, a sub CPU that monitors the main CPU is provided, and the motor drive is stopped when the main CPU is abnormal. Therefore, when the abnormality of the main CPU occurs, continuous control cannot be performed, the power steering function is lost, and the driver has to steer by himself. Further, in Patent Document 3, substitution control is continued as much as possible according to the content of the failure. However, in the case of a CPU abnormality, substitution control is impossible, and it is necessary to steer by itself as in Patent Document 2. did not become.

The present invention has been made to solve such a problem. When a CPU abnormality occurs, this is detected, the drive output of the motor is limited, a minimum power steering function is ensured, and the drive output is limited. An object of the present invention is to provide an electric power steering device capable of stopping the motor drive later.

  An electric power steering apparatus according to the present invention includes a steering torque sensor that detects a steering torque applied to a steering handle by a driver, a motor that supplies power to a steering system and assists a steering force by the driver, and the steering torque sensor includes: In an electric power steering apparatus comprising a CPU that outputs a drive signal for driving the motor in accordance with the detected steering torque, the abnormality of the CPU is monitored and the drive signal for driving the motor is controlled when the CPU is abnormal And a monitoring control means for continuously controlling the motor with a first control mode for stopping the driving of the motor and a temporary driving signal for limiting a driving signal in place of the driving signal of the CPU. When there is a two control mode and the monitoring control means detects an abnormality in the CPU, the monitoring control Selects the second control mode, continuously controls the motor with a provisional drive signal instead of the CPU drive signal, selects the first control mode after the control in the second control mode, and selects the motor The drive is stopped.

  According to the electric power steering apparatus according to the present invention, when an abnormality occurs in the CPU, this is detected, the drive output of the motor is limited, a minimum power steering function is ensured, and the motor drive is performed after the drive output is limited. You can stop. Therefore, even if the CPU malfunctions, the motor drive can be stopped after ensuring the minimum power steering function. Other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention with reference to the drawings.

1 is a block diagram showing an electric power steering device in Embodiment 1 of the present invention. FIG. FIG. 3 is an interlock function diagram according to the first embodiment. 4 is a flowchart for explaining the operation of a sub CPU in the first embodiment. FIG. 6 is a block diagram showing an electric power steering device in a second embodiment. 10 is a time chart of provisional drive signals in the second embodiment. FIG. 10 is a block diagram showing an electric power steering device in a third embodiment. 12 is a time chart for explaining the derivation of a provisional drive signal in the third embodiment. FIG. 10 is a block diagram showing an electric power steering device in a fourth embodiment. 12 is a time chart for explaining the derivation of a provisional drive signal in the fourth embodiment. FIG. 10 is a block diagram showing an electric power steering device in a fifth embodiment. FIG. 10 is an output characteristic diagram of second drive signal generation means in the fifth embodiment. FIG. 10 is a diagram showing an operation of drive signal switching means in the fifth embodiment. FIG. 10 is a block diagram showing another electric power steering apparatus according to Embodiment 5, in which second drive signal generation means is built in a sub CPU. It is a block diagram which shows the electric power steering apparatus in Embodiment 6, and shows another monitoring control circuit. FIG. 10 is a block diagram illustrating a communication monitoring circuit in a sixth embodiment. FIG. 10 is a block diagram showing a timer circuit in a sixth embodiment. FIG. 17 is a waveform diagram for explaining the operation of the timer circuit of FIG. 16 in the sixth embodiment. FIG. 10 is a block diagram showing a torque signal monitoring circuit in a sixth embodiment. FIG. 19 is a waveform diagram for explaining the operation of the torque signal monitoring circuit of FIG. 18 in the sixth embodiment. FIG. 10 is a block diagram illustrating a drive circuit control circuit in a sixth embodiment.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an electric power steering apparatus according to the present invention. A vehicle speed sensor 5, a steering torque sensor 6, and a motor 7 mounted on the vehicle are connected to the control unit 1 of the electric power steering apparatus. The vehicle speed sensor 5 detects the speed of the vehicle and outputs a vehicle speed signal. The steering torque sensor 6 detects a steering torque applied to the steering wheel by the driver and outputs a steering torque signal. The motor 7 provides power to a vehicle steering (steering device) system and assists the steering force of the driver. The control unit 1 is mainly composed of a main CPU (main microcomputer) 2, a sub CPU (sub microcomputer) 3, a drive circuit 4 for the motor 7, and interlock means 8. The main CPU 2 receives a vehicle speed signal from the vehicle speed sensor 5 and a steering torque signal from the steering torque sensor 6, calculates a target drive current for driving the motor 7 in accordance with these information, and generates a drive current signal (drive signal). And the actual drive current is controlled to match the target drive current.

  A drive current signal for driving the motor 7 is output to the line 21 and transmitted to the interlock means 8. For example, as shown in FIG. 2, the interlock means 8 has a drive permission range and a drive prohibition range based on the relationship between the steering torque signal and the drive current signal, and the (steering) torque signal input from the line 31 and the main CPU. When the drive current signal is within the drive permission range, the drive current signal is transmitted to the drive circuit 4 as it is. When the drive current signal is within the drive prohibition range, the drive current signal is limited (for example, the drive of the motor is suppressed or Stop) and move out of the drive prohibition range. That is, the characteristic of the interlock means 8 is to suppress the drive of the motor 7 when the drive current signal of the motor 7 drives the motor 7 in the opposite direction to the direction of the steering torque signal applied to the steering handle. Thus, the drive current signal of the motor 7 is limited.

  The interlock unit 8 has the same drive permission range and drive prohibition range during normal times (when the main CPU is abnormal) and controls the drive current signal, but when there is an abnormality, there is a probability of entering the drive prohibition range. The drive current signal is limited so that the drive current signal is outside the drive inhibition range. Therefore, the drive current signal output from the interlock means 8 becomes a provisional drive current signal when the main CPU 2 becomes abnormal and the drive output to the motor 7 is limited outside the drive inhibition range. In this case, the provisional drive signal is such that when the drive signal of the motor 7 drives the motor 7 in the direction opposite to the direction of the steering torque signal applied to the steering handle, the motor 7 is restrained from being driven. 7 is limited.

  The drive circuit 4 drives the switching element of the H bridge circuit in accordance with the input drive current signal, thereby rotating the motor 7 forward and backward. The drive circuit 4 measures the current flowing through the motor and transmits it as an actual drive current to the main CPU 2 and the interlock means 8 via the line 22. On the other hand, the main CPU 2 and the sub CPU 3 continuously communicate with each other via the line 23, and both the CPUs mutually monitor whether or not their operations are normal. The sub CPU 3 is a monitoring control unit that monitors the abnormality of the main CPU 2 and controls a drive current signal for driving the motor 7 when the main CPU 2 is abnormal. The sub CPU 3 has a first control mode for controlling the motor 7 to stop driving and a second control mode for continuously controlling the motor 7 with a provisional driving current signal instead of the driving current signal of the main CPU.

  When the sub CPU 3 detects an abnormality in the main CPU 2, the sub CPU 3 selects the second control mode, controls the drive circuit 4 via the line 24, and performs temporary drive output from the interlock means 8 in place of the drive current signal of the main CPU. The current signal is allowed to pass and the motor 7 is continuously controlled. Thereafter, when the predetermined condition is satisfied, for example, when the torque signal becomes neutral and the motor stops driving, that is, the sub CPU 3 indicates that the torque signal of the steering torque sensor 6 has become zero via the line 32. When received, the first control mode is selected, the drive circuit 4 is stopped via the line 24, and the operation of the motor 7 is stopped. The predetermined condition may be satisfied, for example, after the sub CPU 3 detects an abnormality of the main CPU 2 and after a predetermined time elapses or when the vehicle speed becomes a predetermined value or less.

  The operation of the sub CPU 3 will be described with reference to the flowchart of FIG. In the flowchart, the error flag EF, the control mode CM, and the drive control DC are used as variables. The error flag EF means whether or not the sub CPU 3 has detected an abnormality of the main CPU 2. When the error flag EF is 0, it is not detected, and when it is 1, it is a detected state. The control mode CM means a control mode of the sub CPU 3. When the control mode CM is 0, the abnormality of the main CPU 2 is not detected. When the control mode CM is 1, the drive circuit 4 is stopped. This is the second control mode in which an abnormality has been detected. The drive control DC means the state of the control signal output from the sub CPU 3 for the drive circuit 4.

  In FIG. 3, step S1 is a variable initialization process, which is executed only once at startup. Here, the error flag EF is set to 0, the control mode CM is set to 0, and the drive control DC is set to drive permission. After executing step S1, the process proceeds to step S2. In step S2, the presence or absence of reception data from the main CPU 2 is checked. If there is reception data, the process branches to step S3, and if there is no reception data, the process branches to step S5. In step S3, a reception process for storing data received from the main CPU 2 in a RAM built in the sub CPU 3 is performed. After executing step S3, the process proceeds to step S4.

  In step S4, the data stored in the RAM in step S3 is compared with predetermined data stored in advance in the ROM built in the sub CPU 3, and if they match, the process branches to step S11 as no received data mismatch. If they do not match, the process branches to step S6 because the received data is inconsistent. The content of the predetermined data held in the ROM built in the sub CPU 3 is the same as the data received by the sub CPU 3 when the main CPU 2 is normal. In step S5, the elapsed time since the last reception from the main CPU 2 is measured, and if the elapsed time continues for 1 second or more, the process branches to step S6. If the elapsed time is less than 1 second, step S11 is executed. Branch to

  In step S6, it is determined from the communication result with the main CPU 2 that there is an abnormality, and the error flag EF is set to 1. After execution of step S6, the process proceeds to step S11. In step S11, the error of the main CPU 2 is determined with reference to the error flag EF. When the error flag EF is 0, it is determined to be normal, and the process branches to step S2, where the error flag EF is 1. When it is determined that there is an abnormality, the process branches to step S12. In step S12, the control mode CM of the sub CPU 3 is determined with reference to the control mode CM. If the control mode CM is 0, it is determined that an abnormality has occurred this time, and the process branches to step S13, where the control mode CM is 0. Otherwise, the process branches to step S14.

  In step S13, the control mode CM is set to 2, and the sub CPU 3 is set to the second control mode. After execution of step S13, the process proceeds to step S2. In step S14, referring to the control mode CM, when the control mode CM is 2, the process branches to step S15, and when the control mode CM is 1, the process branches to step S2. In step S15, the torque signal is monitored. If the torque signal is neutral, the process branches to step S16, and if the torque signal is not neutral, the process branches to step S2. The torque signal neutral is determined to be neutral when the torque signal is in the range of ± 1 Nm. In step S16, the control mode CM is set to 1, the sub CPU 3 is set to the first control mode, the drive control DC is set to drive prohibition, and the drive circuit 4 is stopped. After execution of step S16, the process proceeds to step S2.

  In the conventional apparatus using the sub CPU, the motor drive is immediately stopped when the abnormality of the main CPU 2 is detected. However, in this invention, the sub CPU 3 selects the second control mode and is controlled by the interlock means 8. The provisional drive current signal allows the motor 7 to continue to be driven within a safe range, and after the motor 7 continues to be driven, the motor 7 is stopped. Further, in the conventional apparatus using the interlock means, the interlock means limits the output of the motor, but does not determine the CPU abnormality, so the motor remains in an abnormal state until the driver turns off the ignition key. However, in the present invention, when the predetermined condition is satisfied after the sub CPU 3 selects the second control mode, the first control mode is selected to stop the function of the electric power steering apparatus. Is possible.

Embodiment 2. FIG.
In the first embodiment, when the sub CPU 3 detects an abnormality in the main CPU 2, the sub CPU 3 permits the drive signal output from the interlock unit 8 to pass as a temporary drive signal and restricts the output of the motor 7. After gradually limiting the drive signal, the function of the electric power steering device may be stopped. FIG. 4 is a block diagram showing an electric power steering apparatus according to the second embodiment. In the drawings, the same reference numerals denote the same or corresponding parts, and the description thereof is omitted. Hereinafter, the same applies to each figure.

  The drive signal limiting means 9 outputs a temporary drive signal in which the drive signal of the motor 7 output from the main CPU 2 is limited (reduced) in accordance with the signal of the sub CPU 3 that detects an abnormality of the main CPU 2. The drive signal limiting means 9 does not apply a restriction when the sub CPU 3 has not detected an abnormality of the main CPU 2, but adds a restriction with time when an abnormality is detected and the second control mode is selected. Specifically, as shown in FIG. 5, the drive signal limiting means 9 includes a drive signal for the main CPU 2 input from the line 21 and a drive limit signal input from the line 25 (the sub CPU 3 selects the second control mode). Of the output signal) is calculated and output to the line 26. The sub CPU 3 gradually increases the off-state ratio per unit time of the drive limit signal, so that the electric power The function of the steering device is gradually stopped over time. After the output of the drive signal limiting means 9 is completely stopped (for example, 10 minutes after the sub CPU 3 detects the abnormality), the sub CPU 3 selects the first control mode and switches the drive circuit 4 via the line 24. By stopping, the function of the electric power steering apparatus can be stopped without giving the driver a sudden change in steering force.

Embodiment 3 FIG.
In the second embodiment, the limit of the provisional drive signal is increased as time elapses. However, a vehicle speed signal may be input to the sub CPU 3 and changed according to the signal. FIG. 6 is a block diagram showing an electric power steering apparatus according to the third embodiment. The sub CPU 3 is connected to the vehicle speed sensor 5 and receives a vehicle speed signal. As shown in FIG. 7, each time the sub CPU 3 detects that the input vehicle speed signal is 0, the sub CPU 3 gradually increases the off-state ratio per unit time of the drive limit signal, thereby increasing the electric power. The function of the steering device is gradually stopped.

  That is, the drive signal limiting means 9 calculates the logical product of the drive signal input from the line 21 (the uppermost signal in FIG. 5) and the drive limit signal input from the line 25 (the middle signal in FIG. 7). This is output to the line 26, and every time the sub CPU 3 detects the vehicle speed signal 0 (every time the vehicle speed signal changes), the ratio of the OFF state per unit time of the drive limit signal is gradually increased to The function of the power steering device is gradually stopped. After the output (provisional drive signal) of the drive signal limiting means 9 is stopped (or after it may be considered to be stopped, for example, after the number of detection of the vehicle speed 0 is 4 times), the sub CPU 3 selects the first control mode, By stopping the drive circuit 4 via the line 24, it is possible to stop the function of the electric power steering device without giving the driver a sudden change in steering force. Further, the function of the electric power steering device may be stopped when the output of the drive signal limiting means 9 becomes smaller than a predetermined magnitude.

Embodiment 4 FIG.
In the second embodiment, the limit of the provisional drive signal is increased as time elapses. However, a torque signal may be input to the sub CPU 3 and changed according to the signal. FIG. 8 is a block diagram showing an electric power steering apparatus according to the fourth embodiment. The sub CPU 3 is connected to the torque sensor 6 and receives a torque signal. As shown in FIG. 9, each time the sub CPU 3 detects that the direction of the torque signal is reversed, the sub CPU 3 gradually increases the ratio of the off state per unit time of the drive limit signal, whereby the electric power steering device Realize to stop the function of gradual.

  That is, the drive signal limiting means 9 calculates the logical product of the drive signal input from the line 21 (the uppermost signal in FIG. 5) and the drive limit signal input from the line 25 (the middle signal in FIG. 9). Each time the sub CPU 3 detects that the direction of the torque signal has been reversed (every time the torque signal changes), the ratio of the off state per unit time of the drive limit signal is gradually increased. As a result, the function of the electric power steering apparatus is gradually stopped. After the output (provisional drive signal) of the drive signal limiting means 9 stops (or after it can be regarded as stopped, for example, after 20 times the direction of the torque signal is reversed), the sub CPU 3 performs the first control mode. By selecting and stopping the drive circuit 4 via the line 24, the function of the electric power steering apparatus can be stopped without giving the driver a sudden change in steering force.

Embodiment 5 FIG.
In the first to fourth embodiments, after the sub CPU 3 selects the second control mode, the temporary drive signal based on the drive signal output from the main CPU 2 via the line 21 is used. You may drive the motor 7 based on the drive signal produced | generated by the means independent from CPU2. FIG. 10 is a block diagram showing an electric power steering apparatus according to the fifth embodiment. As shown in FIG. 11, the second drive signal generation means 10 calculates the direction and magnitude of driving the motor 7 according to the (steering) torque signal, and outputs it as a drive signal for the motor 7. When steering to the right, a signal for driving the motor 7 to the right is generated according to the steering torque, and when steering to the left, a signal for driving the motor 7 to the left is generated according to the steering torque. The magnitude of the output signal is set by the DUTY value of a PWM (Pulse Width Modulation) signal.

  When the sub CPU 3 detects an abnormality in the main CPU 2, as shown in the first embodiment, the sub CPU 3 selects the second control mode. A switching signal reflecting the determination result of whether or not the sub CPU 3 has selected the second control mode is input to the drive signal switching unit 11 via the line 27. As shown in FIG. 12, when the switching signal is not in the second control mode, the driving signal switching means 11 selects the driving signal output from the main CPU 2 that is input via the line 21, and in the second control mode. At this time, the drive signal output from the second drive signal generation means 10 input via the line 28 is selected and output to the line 29. By using the drive signal switching means 11, the provisional drive signal does not depend only on the main CPU 2, so that more stable steering assist torque can be generated when the sub CPU 3 selects the second control mode.

  In the block diagram shown in FIG. 10, the second drive signal generation means 10 is described as being independent of the sub CPU 3, but may be built in the sub CPU 3 as shown in FIG.

Embodiment 6 FIG.
In the first to fifth embodiments, the main CPU 2 is monitored, and the sub CPU 3 is used as a monitoring control unit for controlling a drive signal for driving the motor 7 when the main CPU 2 is abnormal. 14 is obtained by replacing the sub CPU 3 of the first embodiment with a monitoring control circuit 41. The monitoring control circuit 41 includes a communication monitoring circuit 42, a torque signal monitoring circuit 43, and a drive circuit control circuit 44. Note that communication with the main CPU 2 is performed only for reception.

  As shown in FIG. 15, the communication monitoring circuit 42 includes a timer circuit 421, a RAM 422, a ROM 423, a comparator 424, an error determination circuit 425, and an output holding circuit 426. A reception signal from the main CPU 2 is input to the timer circuit 421 and the RAM 422 via the line 23. As shown in FIG. 16, the timer circuit 421 discharges the charge accumulated in the capacitor C1 when the reception signal from the main CPU 2 inputted from the general CR circuit 421a and the line 23 changes from L to H. And a determination circuit 421c for setting the output to H when the potential of the capacitor C1 becomes larger than a predetermined value T set by the resistors R1 and R2. Here, the predetermined value T is a time (for example, 1 second) in which it can be reliably determined that the state is abnormal.

  As shown in FIG. 17, the potential of the capacitor C1 of the CR circuit 421a increases with time, but when there is a reception signal from the main CPU 2, the transistor Tr1 of the reset circuit 421b is turned on and the potential is lowered. However, when there is no reception signal from the main CPU 2, the potential of the capacitor C1 continues to increase and exceeds the predetermined value T, so that the output of the determination circuit 421c becomes H. Accordingly, if H of the output of the determination circuit 421c is 1 and L is 0, if there is a reception signal from the main CPU 2 between the past time corresponding to the predetermined value T and the current time, 0 is output to the line 33. When there is no reception signal, the timer circuit 421 that outputs 1 to the line 33 can be realized.

  As shown in FIG. 15, the received signal from the main CPU 2 is stored and held in the RAM 422. The ROM 423 is a memory that stores in advance data to be transmitted by the main CPU 2 when it is normal. The comparator 424 compares the RAM 422 and the ROM 423, outputs 0 if they match, and outputs 1 if they are different. Thereby, when the data transmitted from the main CPU 2 is normal, the output of the comparator 424 becomes 0, and when the data transmitted from the main CPU 2 is abnormal, the output of the comparator 424 becomes 1.

  The error determination circuit 425 performs an OR operation on the output of the timer circuit 421 and the output of the comparator 424 and outputs the result. The output holding circuit 426 is an SR flip-flop circuit that holds the output Q when the signal input to the input S is 0, and sets the output Q to 1 when the signal input to the input S is 1. It is configured. Note that the output Q of the SR flip-flop circuit is initialized to 0 when the system is started. Thus, when the main CPU 2 regularly transmits normal data, 0 is output. When the data transmitted by the main CPU 2 is abnormal, or when the main CPU 2 does not transmit data, 1 is output. Thereafter, the communication monitoring circuit 42 that holds the state of outputting 1 is realized.

  The torque signal monitoring circuit 43 includes a window comparator as shown in FIG. The voltage set by the resistors R3 and R4 is a predetermined value TrqH, and the voltage set by the resistors R5 and R6 is a predetermined value TrqL. Here, it is assumed that the predetermined value TrqH is a value higher than 0 N · m (for example, 1 N · m) in terms of torque signal, and the predetermined value TrqL is a value lower than 0 N · m (for example, −1 N · m) in terms of torque signal. When the torque signal input via the line 32 is smaller than the predetermined value TrqH and larger than the predetermined value TrqL, the output of the torque signal monitoring circuit 43 becomes H. Further, when the torque signal is larger than the predetermined value TrqH, or when the torque signal is smaller than the predetermined value TrqL, the output of the torque signal monitoring circuit 43 becomes L.

  Therefore, when the output H of the circuit is 1 and L is 0, as shown in FIG. 19, when the torque signal is neutral (between the predetermined value TrqH and the predetermined value TrqL), 1 is output to the line 34, When the torque signal is out of neutral, the torque signal monitoring circuit 43 that outputs 0 to the line 34 can be realized.

  The drive circuit control circuit 44 includes an AND circuit 44a and an output holding circuit 44b as shown in FIG. The signal input from the line 33 and the signal input from the line 34 are ANDed by the AND circuit 44a and output to the output holding circuit 44b. The output holding circuit 44b is configured by an SR flip-flop circuit that sets the output Q to hold the previous value when the signal input to the input S is 0, and sets the output Q to 1 when the signal input to the input S is 1. ing. Note that the output Q of the SR flip-flop circuit is initialized to 0 when the system is started. The output Q is output to the drive circuit 4 via the line 24.

  With the above configuration, when the reception data from the main CPU 2 is abnormal or when reception is interrupted, the state is held as the second control mode, and when the torque signal becomes neutral, the first is sent via the line 24. A function equivalent to that of the sub CPU 3 of the first embodiment that stops the drive circuit 4 as the control mode can be realized.

  It should be noted that within the scope of the present invention, the embodiments can be freely combined, or the embodiments can be appropriately modified or omitted.

An electric power steering apparatus according to the present invention includes a steering torque sensor that detects a steering torque applied to a steering handle by a driver, a motor that supplies power to a steering system and assists a steering force by the driver, and the steering torque sensor includes: In an electric power steering apparatus comprising a CPU that outputs a drive signal for driving the motor in accordance with the detected steering torque, the abnormality of the CPU is monitored and the drive signal for driving the motor is controlled when the CPU is abnormal And a monitoring control means for continuously controlling the motor with a first control mode for stopping the driving of the motor and a temporary driving signal for limiting a driving signal in place of the driving signal of the CPU. When there is a two control mode and the monitoring control means detects an abnormality in the CPU, the monitoring control Selects the second control mode, continuously controls the motor with a provisional drive signal instead of the CPU drive signal, selects the first control mode after the control in the second control mode, and selects the motor The monitoring control means selects the first control mode when the provisional drive signal becomes smaller than a predetermined value when the second control mode is selected. The driving of the motor is stopped .
The electric power steering apparatus according to the present invention includes a steering torque sensor that detects a steering torque applied to a steering wheel by a driver, a motor that supplies power to a steering system and assists a steering force by the driver, and the steering torque. In an electric power steering apparatus comprising a CPU that outputs a drive signal for driving the motor in accordance with a steering torque detected by a sensor, the drive signal for monitoring the CPU abnormality and driving the motor when the CPU abnormality occurs Monitoring control means for controlling the motor, and the monitoring control means continuously controls the motor with a first control mode for stopping the driving of the motor and a provisional driving signal for limiting a driving signal in place of the driving signal of the CPU. And when the monitoring control means detects an abnormality in the CPU, the monitoring control means The control means selects the second control mode, continuously controls the motor with a provisional drive signal instead of the CPU drive signal, and selects the first control mode after the control in the second control mode. The provisional drive signal is for stopping the motor drive, and the motor drive signal output from the CPU is opposite to the direction of the steering torque applied to the steering handle. When the motor is driven, the drive signal of the motor is limited so as to suppress the drive of the motor.
Furthermore, the electric power steering apparatus of the present invention includes a steering torque sensor that detects a steering torque applied to the steering handle by the driver, a motor that supplies power to the steering system and assists the steering force by the driver, and the steering torque. In an electric power steering apparatus comprising a CPU that outputs a drive signal for driving the motor in accordance with a steering torque detected by a sensor, the drive signal for monitoring the CPU abnormality and driving the motor when the CPU abnormality occurs Monitoring control means for controlling the motor, and the monitoring control means continuously controls the motor with a first control mode for stopping the driving of the motor and a provisional driving signal for limiting a driving signal in place of the driving signal of the CPU. And when the monitoring control means detects an abnormality of the CPU, the monitoring control means The control means selects the second control mode, continuously controls the motor with a provisional drive signal instead of the CPU drive signal, and selects the first control mode after the control in the second control mode. Stopping the driving of the motor,
The provisional drive signal is a signal that restricts the drive signal of the motor output from the CPU so as to reduce the drive signal. A drive signal limiting unit is connected to the CPU, and the drive signal The limiting means limits the motor drive signal output from the CPU with a signal when the second control mode is selected by the monitoring control means to obtain the provisional drive signal.

Claims (11)

A steering torque sensor for detecting a steering torque applied to the steering handle by the driver, a motor for supplying power to the steering system and assisting the steering force by the driver,
In an electric power steering apparatus comprising: a CPU that outputs a drive signal for driving the motor according to a steering torque detected by the steering torque sensor;
The monitoring control means for monitoring the CPU abnormality and controlling a drive signal for driving the motor when the CPU abnormality occurs,
The monitoring control means has a first control mode for stopping the driving of the motor and a second control mode for continuously controlling the motor with a provisional driving signal for limiting a driving signal in place of the driving signal of the CPU.
When the monitoring control means detects an abnormality of the CPU,
The monitoring control means selects the second control mode, continuously controls the motor with a provisional drive signal instead of the CPU drive signal, and selects the first control mode after the control in the second control mode. An electric power steering apparatus characterized in that the driving of the motor is stopped.   The monitoring control means selects the first control mode and stops driving the motor when the time during which the second control mode is selected becomes longer than a predetermined time. The electric power steering device described in 1.   The monitoring control means selects the first control mode and stops driving the motor when the provisional drive signal becomes smaller than a predetermined value when the second control mode is selected. The electric power steering apparatus according to claim 1.   The provisional drive signal is used to drive the motor when the motor drive signal output from the CPU drives the motor in a direction opposite to the direction of the steering torque applied to the steering handle. 2. The electric power steering apparatus according to claim 1, wherein a drive signal of the motor is limited so as to be suppressed.   2. The electric power steering apparatus according to claim 1, wherein the provisional drive signal imposes a limitation on the drive signal of the motor output from the CPU so as to reduce the drive signal. An interlock means is connected to the CPU,
The interlock means has a drive permission range and a drive prohibition range based on a relationship between the steering torque and the drive signal output by the CPU, and when the steering torque and the drive signal are within the drive permission range, The drive signal is transmitted as it is, and when it is within the drive prohibition range, the drive signal is limited so as to be outside the drive prohibition range,
When the monitoring control means selects the second control mode and continuously controls the motor with a provisional drive signal in place of the CPU drive signal, the monitoring control means is limited to be outside the drive inhibition range by the interlock means. The electric power steering apparatus according to any one of claims 1 to 5, wherein the motor is continuously controlled by a provisional drive signal.   Drive signal limiting means is connected to the CPU, and the drive signal limiting means limits the motor drive signal output from the CPU by a signal when the second control mode is selected by the monitoring control means, 6. The electric power steering apparatus according to claim 5, wherein the provisional drive signal is obtained.   The drive signal limiting means gradually reduces the motor drive signal output from the CPU with the passage of time by a signal when the second control mode is selected by the monitoring control means to obtain the provisional drive signal. The electric power steering apparatus according to claim 7.   The drive signal limiting means gradually lowers the motor drive signal output from the CPU with a change in the vehicle speed signal of the vehicle speed sensor by a signal when the second control mode is selected by the monitoring control means, 8. The electric power steering apparatus according to claim 7, wherein a provisional drive signal is obtained.   The drive signal limiting means gradually decreases the motor drive signal output from the CPU with a change in the steering torque by a signal when the second control mode is selected by the monitoring control means, so that the provisional drive is performed. 8. The electric power steering apparatus according to claim 7, wherein a signal is obtained. Along with the CPU that outputs a drive signal for driving the motor according to the steering torque detected by the steering torque sensor,
Drive signal generating means for outputting a drive signal for driving the motor according to the steering torque is provided,
When the monitoring control unit detects an abnormality in the CPU, a driving signal output by the driving signal generation unit is selected as a driving signal for driving the motor according to a signal when the second control mode is selected by the monitoring control unit. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is a provisional drive signal.

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